Orthrus

Orthos (Greek Ὀρθός ) or Orthros, figure of Greek mythology, is a dog with two heads.

He was brought into the world of Typhon, a giant with a hundred dragon or snake heads, and Echidna, a monster that was half woman and half snake. Had Orthos - so the Theogony of Hesiod - five siblings: Kerberos, the Chimera, the Hydra, the Nemean Lion and the begotten by himself with the mother Sphinx. He guarded the island Erytheia the cattle of Geryon. Herakles, whose job it was tenth, the latter to steal, killed Mr. and dog and drove away the flock.